public class Main {
    public static void main(String[] args) {
        AdvertisementBoard advertisementBoard = new AdvertisementBoard();
        advertisementBoard.show();
        advertisementBoard.setAdvertisement(new BlackLandCorp());
        advertisementBoard.show();
        advertisementBoard.setAdvertisement(new WhiteCloudCorp());
        advertisementBoard.show();
    }
}